The liquid dessicant gas dehydrator has been around the oil patch for decades. Glycol has been the preferred liquid dessicant from the beginning. Slowly the glycols have been improved to enable higher heat levels to boil off higher percentages of water the glycol absorbs from gas. Improvements to the absorber tower, in which the gas to be dried is contacted by the glycol, have been made in fits and starts. The reconcentrator for the glycol has also been improved over the years. A notable leap forward was made in "gas stripping" the gylcol, after thermal reconcentration, as disclosed in U.S. Pat. No. 3,105,748 Stahl issued Oct. 1, 1963.
Parallel with glycol dehydrator evolution, was concern with the low temperatures in the upstream gas-liquid separator as the high pressure of the streams produced from their wells was reduced toward the pressure values of transmission lines. Of course the conservationists puzzle over how to use the energy of the high pressure fluids released by the pressure reduction. A separate, well-identified section of the prior art was developed around this problem. But a very important concern to the oil field operator was with the hydrates and solidifying wax in his separator vessel as the temperature within the vessel dropped during the pressure reduction. The operator wanted heat to keep his fluid flowing through his separator toward the point of sales.
Separator vessels were moved downstream to the glycol dehydrator as a source of heat. U.S. Pat. No. 2,735,506 Glasgow issued Feb. 21, 1965 to represent this evolution. A common wall between the two vessels enabled the heated glycol being reconcentrated to transmit heat into the separating fluids of the separator vessel. This particular feature of the trend twenty years ago did not continue. However, within ten years a heated body of water was thermosiphonically circulated through a coil in the liquids of a gas-liquid separator. U.S. Pat. No. 3,119,674 Glasgow et al. issued Jan. 28, 1964 to represent these systems. It did not take long for those skilled in the art to pipe the heated glycol of the downstream dehydrator to the upstream gas-liquid separator. U.S. Pat. No. 3,206,916 Glasglow et al. issued Sept. 21, 1965 to represent this technology.
At the classic oil-field pace of thinking, the stage was set for the next combination of gas-liquid separator and liquid dessicant dehydrator. The workers in this particular art are on the move to find the structural combination which will reduce the complexity of the connecting concommitant vessels and at the same time utilize heat exchange between the fluids in the vessels to preserve and improve the process of separating the fluids and moving them to market. More specifically, there are many wells producing gas in the range of 250,000 scfd to 2 MM scfd with liquids having a range including 10 bbl/mm scf of gas. The pressure of production may be near 1550 psig and the temperature near 100.degree. F. The transmission line pressure is in the neighborhood of 350 psig and the temperature desired is 60.degree. F. to 80.degree. F. The dewpoint depression required for the undersaturated gas is not severe: 70.degree. to 80.degree. depression. How can the separator vessel and part of the glycol dehydration system be combined to reduce the complexity of vessel interconnection and provide the heat of the reconcentrated dessicant to prevent hydrates and paraffin solidification in the separator vessel?